704
AWUS01 KWNH 190431
FFGMPD
NCZ000-SCZ000-190730-

Mesoscale Precipitation Discussion 0290
NWS Weather Prediction Center College Park MD
1231 AM EDT Sun May 19 2024

Areas affected...Northern South Carolina... Adj. Southeastern
North Carolina...

Concerning...Heavy rainfall...Flash flooding possible

Valid 190430Z - 190730Z

SUMMARY...Slow to stationary thunderstorms along old frontal
boundary may produce spots of 2-3" in short-duration posing
localized possible flash flooding incidents.

DISCUSSION...Regional RADAR and 10.3um EIR loop depicts an
west-east line across northern SC erupting in low-topped showers
generally west of the subtropical jet axis paralleling the
Atlantic coast.  Surface to boundary layer analysis denotes solid
FGEN ascent due to directional convergence as this older boundary
drops south but continues to tighten within temperature/moisture
fields.  While instability is limited, MLCAPE of 500-750 J/kg and
is sufficient given the convergence for this development.

CIRA LPW/GOES-WV notes that inner core moisture in proximity and
downshear of the slow moving closed low in the southern Cumberland
Plateau has stretched through the deformation/effective TROWAL
through the common Carolina boarder, adding to the overall
moisture available for the weak showers.  Total PWATS of 1.5-1.75"
are enhanced with limited mid-level loss to evaporation.  As such,
efficient rain showers with rates of 1.5-1.75" are probable.  Deep
layer steering is weak under this col in flow but is also
generally parallel to the boundary at 5-10kts toward the east.
This may allow for some slow training, but the duration of cells
may only last 1-2 hours given the limited instability.  As such,
localized spots of 1.5-2.5" are possible with maybe a spot of 3"
not unreasonable.

Hydrologically, the area has been slightly above normal in
saturation per NASA SPoRT LIS 0-40cm soil depth information and 7
day precipitation anomalies bare this out with pots of 200-300% of
normal north of the I-26 between Columbia and Florence, SC but
also extending back toward Spartanburg.  So while 1hr and 3hr are
between 1.5-2" and 2-3", respectively; there remains a possibility
of exceedance, especially along just west of the Fall-line where
increased run-off may result in incidents of localized flash
flooding along this axis over the next few hours.

Gallina

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...CAE...GSP...ILM...

ATTN...RFC...SERFC...NWC...

LAT...LON   35098228 34868124 34687996 34617948 34417848
            34137853 34007917 34078037 34138097 34418221
            34678282 34918295 35058276